Technical Field
The present invention relates to a concentrator for microorganisms existing in water, and, for example, relates to a microorganism concentrator that can recover microorganisms in a living state included in ballast water, river water, or the like.
Background Art
To check the number of microorganisms in a living state included in ballast water, devices for concentrating microorganisms existing in the ballast water have been proposed (for example, see Patent Literature 1).
FIG. 4 illustrates a microorganism concentrating device that is disclosed by Patent Literature 1.
In the device disclosed by Patent Literature 1, a filter cloth 303 in a substantially inverted cone shape is set in a water storage container 300, a space 300A outside the filter cloth 303 is separated from a space 300B inside the filter cloth 303, an overflow pipe 312 and a drain port 313 are placed in the space 300A outside the filter cloth 303, and a lower-end opening 303b of the filter cloth 303 is connected with a reservoir 304.
According to the device disclosed by Patent Literature 1, when supply of sample water to the inside of the filter cloth 303 is continued, water in the water storage container 300 overflows from the overflow pipe 312 so that the sample water W2 moves from the inside to the outside of the filter cloth 303. Consequently, the number of aquatic organisms that are too large to pass through the filter cloth 303 increases in the space 303B inside the filter cloth 303.
After a predetermined amount of the sample water is supplied to the inside of the filter cloth 303 and the supply of the sample water is stopped, water in the water storage container 300 is drained from the outlet 313. Accordingly, the sample water moves from the inside to the outside of the filter cloth 303 to be drained from the drain port 313 so that concentrated water W3 including concentrated aquatic organisms that are too large to pass through the filter cloth 303 is stored in the reservoir 304 in the space 303B inside the filter cloth 303.
In the device disclosed by Patent Literature 1, when sample water moves from the inside to the outside of the filter cloth 303, aquatic organisms that are too large to pass through the filter cloth 303 hit against the inner surface of the filter cloth 303 and adhere to the inner surface of the filter cloth 303.
Pressure due to the movement of the sample water is applied to the aquatic organisms adhering to the inner surface of the filter cloth 303. However, since the filter cloth 303 has a substantially inverted cone shape that is a tapered shape, pressure of the self-weight in a vertically downward direction is further applied to the aquatic organisms.
Consequently, in the device disclosed by Patent Literature 1, aquatic organisms adhering to the inner surface of the filter cloth 303 are considerably damaged. Therefore, there is a possibility that most of the aquatic organisms die and cannot be recovered in a living state.